also create manifest for devices with BROKEN=1, if we have the images

`make manifest` does not take the `BROKEN=1` parameter, like other build
commands do.
But it seems the underlying `scripts/target_lib.lua` does get this info
from the environment anyway. So we can pass that info, bypassing the
makefile.

builder.sh

@@ -148,7 +148,7 @@ done
 # build manifest
 # ##############
 echo making manifest
-make manifest GLUON_AUTOUPDATER_BRANCH=$BRANCH GLUON_PRIORITY=${PRIO} GLUON_RELEASE=${RELEASENAME}
+BROKEN=1 make manifest GLUON_AUTOUPDATER_BRANCH=$BRANCH GLUON_PRIORITY=${PRIO} GLUON_RELEASE=${RELEASENAME}
 
 
 # write the current site-commit as into-text